1. Field of the Invention
The invention relates to a coupling member, in particular, a pipe-shaped socket, for connecting a part, provided for receiving or dispensing fuel and made primarily of HDPE (high-density polyethylene), to a fluid line, wherein the coupling member has first, second, and third component of primarily meltable material, in particular, thermoplastic material, of which the third component forms a heat fusion joint with the fuel-carrying part and has an undesirably high permeability and swelling capacity relative to fuel and is connected to the first component in a material-bonding and/or positive-locking way, while the second component has a greater blocking capacity relative to fuel and a higher strength than the third component. The invention is also directed to a method for manufacturing the coupling member.
2. Description of the Related Art
In a known coupling member (DE 195 35 413 C1) of this kind the first and second components have a high impermeability with regard to diffusion of fuel, such as gasoline or diesel fuel, but not the third component which is welded or fused to the fuel-carrying part, i.e., the fuel tank. The material of the third component must always be selected such that it can form a heat fusion joint or connection with the fuel tank that is generally primarily made of—at least its outer layer—HDPE (high-density polyethylene); HDPE is not sufficiently impermeable with respect to diffusion of fuel. The amount of fuel which diffuses per time unit through the third component is minimal but can not be neglected over an extended period of time. Moreover, the material of the third component has an undesirably high swelling capacity relative to fuel and minimal tearing strength. When the material swells, the coupling member can tear off the tank.